This invention relates to digital copying machines in which picture cell data are processed after being digitalized, and more particularly to a density correcting system in the digital copying machine.
In a conventional copying machine according to an electrostatic process, the copy density is corrected by changing the exposure slit width according to indication specified by a density correcting knob on the operating panel.
In a conventional copying machine according to a diazo process, the copy density is corrected by changing the time required for applying light to a photo-sensitive material, i.e., by changing the rate of feeding a copying sheet.
In some of the copying machines according to a development process, the density is increased by adding a developer when lowered.
In these conventional density correcting methods, the copy density is, in its entirety, changed. Therefore, when the density is increased, the background becomes stained.
In the method of changing the rate of feeding a copying sheet, the copying speed is not constant. Therefore, this method is disadvantageous in that the copying speed is liable to be low.
In the method of changing the density by supplementing the developer, the rate of changing the density is low.